Deployment of long aperture arrays using large numbers of sensor elements has been enabled by the evolution of sensor technology, telemetry technology, and digital processing technology. Such arrays hold promise for benefits in terms of theoretical processing gain and spatial resolution. Long aperture arrays have been employed across a range of applications, including acoustic and radar applications. Adaptive beamforming techniques have been applied to long aperture arrays to increase a system's ability to perform well in complicated signal and interference environments. For many adaptive beamforming techniques, increasing the number of sensor elements of the array works against a desire to adapt quickly. Additionally, multipath environments introduce challenges that may cause substantial performance loss for certain adaptive beamforming techniques.
Many approaches for covariance estimation for adaptive beamforming have been proposed. Many adaptive beamforming techniques use sensed data to estimate a covariance matrix and use the covariance matrix for spectral estimation. However, snapshot deficient operation and correlated signal and interference environments continue to be difficult to handle for certain adaptive beamforming techniques.